The filters of air cleaners must be periodically replaced or cleaned to prevent undue buildup of dust and particulate matter which would adversely affect proper operation. Pulse-jet cleaners are typically used in installations requiring treatment of large volumes of air. Cleaning is accomplished by pulsing air through the filters in a direction opposite to the normal airflow direction to effect self-cleaning during operation of the system without removal and replacement of the filters. For example, U.S. Pat. No. 4,331,459 to Donaldson Company, the assignee hereof, shows a self-cleaning pulsed air cleaner which operates on this principle.
Such pulse-jet air cleaners usually include a reservoir or tank of compressed air which is connected by a diaphragm valve to a nozzle or orifice positioned to direct the air against the filter to effect cleaning. The diaphragm valve is controlled by a pilot valve. The air tank is charged with ambient air drawn from atmosphere by a compressor. However, the moisture content of the ambient air depends upon the season, temperature, etc. Therefore, as the air is pressurized and cooled, condensate or moisture tends to accumulate in the tank which can adversely affect operation of the pulse-jet air cleaner and lead to corrosion of the tanks.
The accumulation of moisture in the compressed air tanks of pulse-jet air cleaners has been a long-standing problem. Dryers are sometimes used to dry the incoming air. These are expensive, however, and require additional maintenance and space. More typically, some form of manual or automatic drain valve is incorporated into the tank. Such drain valves only operate intermittently and the intervals between operation necessary to minimize moisture accumulation in the tank vary depending upon the pressure, temperature and humidity of the ambient air. Thus, excessive amounts of moisture can accumulate in the tank when drain valves are used, causing reduced cleaning effectiveness or increased tank corrosion. Further, drain valves must remain open long enough for drainage of any moisture accumulation, which in turn also releases at least some pressure from the tank. A simple, staightforward means for removing moisture on a relatively continuous, automatic basis has not been available heretofore.
A need has thus arisen for an apparatus for automatically removing moisture accumulated inside compressed air tanks on a relatively continuous basis without manual interaction, or expensive modifications or additional components.